A Canadian company, Over the Edge, will coordinate the rappelling -- and the insurance for the event -- in which participants are harnessed to ropes and do a controlled descent down the outside of the building.

The system is the same as those used by mountain climbers.

Over the Edge recently did a similar event at a building opening in Atlanta.

A topping out ceremony for River House is planned for Wednesday, when the final steel beam with a traditional fir tree atop it is expected to be hoisted into place.

The invitation-only party for about 400 people will mark the end of vertical construction on the tower's 34-floor condominium project.

Grooters was jubilant as he reflected on the project as it nears completion. The first occupants are expected to move in by mid-October.